Tear stains on dogs are often caused by porphyrins, which are iron-carrying molecules that are the by-product of red blood cells being broken down. Porphyrins are carried in a dog’s tears, urine, and saliva, and when they come into contact with the pet’s fur, stains are produced. “The chemical reaction between porphyrins and fur is what causes the change in color,” says Zay Satchu, DVM, chief veterinary officer and co-founder of BondVet, based in New York City. In this case, the extent of a dog’s tear stains is determined by the quantity of porphyrins and tears produced by the individual pet, says Rachel Ann Stalcoskie, head stylist and co-owner of Rachel Ann’s Country Clips Pet Grooming in Pocono Summit, Pennsylvania. Tear stains on white dogs are typically more obvious but only because of their light fur. While tear stains on dogs are harmless, they may be indicative of an underlying medical issue. So, “If tear stains are a new development, it is a good idea to have a physical exam performed by a veterinarian to ensure there is no medical reason causing increased tear production that is leading to the staining,” recommends Dr. Satchu. Tear stains on dogs are sometimes due to either eye irritation or a tear duct system that doesn’t drain tears correctly. Normally, tears drain from the eyes to the nose—but a wonky tear duct system causes tears to flow over the eyelid and onto the face. What are some of the other things that may cause tear stains that your vet might want to rule out? Entropion: This is where the eyelids are positioned towards the eye instead of away. Some breeds, including English Bulldogs, Great Danes, and Miniature Poodles, are more susceptible. A yeast or fungal infection Abnormal eyelashes: Ectopic cilia, for example, occurs when one or more hairs grow abnormally. The hair then makes contact with the cornea (surface of the eye) and causes irritation and ulcers. Damage to the cornea: This is oftentimes caused by an infection or the result of an injury to the eye. Glaucoma: When fluid builds up, it increases pressure on the eye.,Jump to section What Causes Tear Stains on Dogs? How To Get Rid of Tear Stains on Dogs How To Prevent Tear Stains on Dogs